Molecular sieves are crystalline materials which have distinct crystal frameworks with ordered pore structures and cavities. Aluminosilicate zeolite-type molecular sieves useful as adsorbents or catalysts are known in the art and now comprise over 150 species of both naturally occurring and synthetic compositions. In general, the zeolites have frameworks formed from AlO.sub.4 -and SiO.sub.4 tetrahedra joined by the sharing of oxygen atoms. Such zeolites have a significant ion-exchange capacity and are capable of reversibly desorbing an adsorbed phase which is dispersed through the internal voids of the crystal without displacing any atoms which make up the permanent crystal structure.
Non-zeolite molecular sieves comprising aluminophosphates are also known to be useful as adsorbents or catalysts. These non-zeolite molecular sieves generally contain [AlO.sub.2 ] and [PO.sub.2 ] tetrahedral units as essential framework constituents, and at least one additional element as a framework tetrahedral unit.
Various catalysts are known for their use in the double bond isomerization of olefinic feed compounds. However, many of these catalysts produce substantial amounts of polymer and/or skeletal isomerized product, i.e., branched olefins. For some applications, such as preparing internal olefins for alkylation reactions, it is desirable to limit branched products to the least amount possible. Therefore, for certain applications, it is desirable to use a catalyst which is selective for the isomerization of the double bond without the isomerization of the skeletal structure.